NP, AP, VO2 intervals, etc

trijedi

What's the point of being on a forum if you can't indulge in a little overthinking on occasion? With that out of the way...

 

My VO2 rides are outside which sounds lovely but turns out to make them more difficult. Several times I have had to slow when people get in the way. One time a young child (riding behind a parent) decided to just stop and get off her bike and move to the middle of the bike path. Argghh. After slowing, I then hammer to try to get the AP back to where it needs to be. Sometimes, I don't make it but my NP is still higher than 20% of my FTP, I think. That is the first question.

 

1. WKO 2.2 gives an IF for intervals as short as 2.5 minutes although it doesn't give the NP. Is that intensity a valid measure? or should AP be the metric to consider for short intervals?

 

I've noticed that I can nail these VO2 intervals easily if I do them climbing. Back on the flats, it is not nearly so easy. I'm surmising that there is a neuromuscular component (I can't pedal fast enough) that I need to train to put out more power on the flat. So the second question.

 

2. Is it "better" to do the VO2 intervals on the flat? Is "work work" so it doesn't matter?

 

Rubin

Scott Alexander

1) Anything that short, just use your PAvg. I think that's what most peeps around here (including me) have been doing.

2) IMO, if you hit the power targets, it's the same workout. However, like the drainer, try to get your cadence up so you're not grinding.

Nemo Brauch

Caution! Over reaching the VO2 interval to play "catch up" on your AP can be very dangerous. If you have to slow down to let a kid, squirrel, old lady, whatever cross the road, do so. But do not exceed the %FTP guidance in order to bring that AP back up again. That's a dangerous game and could dig a hole of hurt that's much harder to come out of in the end. Just return to the perscribed FTP% when the coast is clear and finish the interval. FWIW- that's why many of us do VO2 stuff on the trainer even in good weather- it's just safer in some cases.

In reviewing the WKO data after the ride, the only data you'll have on these short intervals is AP.

No problem using the hills to help with these VO2 sets- as long as you have enough road to finish out the interval before the downhill comes (much harder to maintain VO2 on a downhill)

Dave Campbell

I've thought about the question of using a long hill to do these. I'm not sure a watt is a watt in this case though. Say FTP is 200, then 120% would be 240. If 240 @ 60 rpm is the same as 240 at 90, then whats the value of the quadrant analysis and the science that goes with that. I've done several mountain centuries where climbs last 1 hour or more at 7-8%. Power will be at FTP, but at 60rpms. Doesn't seem nearly as taxing as a 1 hour TT at 90rpms from a cardio perspective, but I would hate to even try to run after one of those climbs. So, since I want to race around 85+ cadence, I do this stuff on the trainer. That way I'm in better control of the conditions. Am I missing something with this plan?

William Jenks

WKO doesn't let you get a NP for short intervals because it has to average the power data. When you raise the power data to the 4th power, very short data spikes would make the NP pretty meaningless if you didn't. However, the averaging system means that it boogers the first part of the interval. For a segment that is sufficiently long, it makes virtually no difference. If the interval is sufficiently short, it can mess up the calculation enough that the AP just makes more sense.  The folks at WKO just decided to make the calculation "not work" for less than 2.5 minutes or whatever it is to get around this issue.



If you really want NP for a short interval, I'm pretty sure Power Agent does it.

trijedi

@Nemo and William

I understand why NP can get weird for short periods (sampling, data spikes, and start up values for the rolling 30 second average). I also know that they don't ooutput a value for short intervals, however, in WKO 2.2 (I've never upgraded to 3.0), they still output the intensity factor IF. Since IF = NP/AP, they have implicitly provided the NP... It only matters in the sense that for those slightly interrupted intervals, I hit the numbers using NP although I may slightly miss using AP.

@Dave

I am lucky to have a 3 mile long hill. It was overcast today so instead of riding 15 minutes to the bike trail and perhaps have to ride back in the rain, I rode 5 minutes to the hill and popped out 5x(2.5',2.5'). I had to ride downhill on one of the easy periods. The RPE is so much lower climbing than it is on the flats that it seems too good to be true.

 

@Scott, Dave

When climbing this ~5% grade, I have been varying my cadence. Some intervals were at 60; others were at 80+. On the flats, I've been doing them between 80 and 95. Even at the same cadence, it seems that it is easier for me to put out more power while climbing.

 

So, I guess that the consensus is that the important thing is to do the work - hills, flat, or trainer. Still, I think I'll do more of these VO2 workouts on the flat. There must be some other physiological (or mental?) system that I need to train so that I can push as hard on the flat as I can climbing.

 

Al Truscott

Flats vs hills for VO2 intervals: I'm scared of doing V)2 intervals outside, except on a steep hill. On the flats, I'd have to be going 25+ mph for 2.5 minutes, or a mile. Too much can happen, in a dangerous sense, out on the road while I'm focused on extreme effort. On the kind of steep (8-12%) hills I have around here, I can work hard, go 8-10 mph, and feel very safe. Plus, it DOES feel easier, at the same watts, when going uphill.

To anyone doing FTP or VO2 intervals on a multi-use path, with dogs, old ladies, small kids in trikes, etc around, I'd say, gently, "Don't". It's just not safe for all concerned.

Spokane_Al

To anyone doing FTP or VO2 intervals on a multi-use path, with dogs, old ladies, small kids in trikes, etc around, I'd say, gently, "Don't". It's just not safe for all concerned.

I second Al's comments. Please be careful out there - for your sake and that of all the other shapes, sizes, speeds, capabilities and species using any multi use trail, path or road.

Bill McKinney

3rd for Al and Al's comments. Doing any intervals on a recreational pass is crazy for you and for the other folks on the path. If you do them on a path, though, as an insurance guy I would suggest 2 things. 1 - make sure your health insurance is up to date in case you crash. 2 - make sure you've got at least a $1-2 million liability umbrella...if you crash into the kid that stopped in the middle of the path and they get a brain injury, you'll lose your cash savings, your 401K, your IRAs, and maybe your house depending on where you live to cover the cost of their medical care for the kid. I know a family who had this happen when their 18 year old hit a biker with their car...those liability limits you have with your auto insurance are pretty small when you're facing lifetime care for a catastrophic brain injury, and you ARE on the hook for it if you've got the $$.

trijedi

@Al and Al

Sounds like good advice. The trail is the San Gabriel River Bike Trail. Most of my FTP and VO2 rides are during weekday early afternoons when it is mostly empty except for other cyclists. On weekends, it is a bit more crowded.

 @Bill - More good advice.

jetskr

Bill, great advise. That's not something most people think about.

Coach Rich

Fine to do this stuff, or interval training of any flavor, on a hill. And don't worry too much about cadence on these. Yes, intervals on a hill are "different" from on a flat, but in general I find them to be safer, easier mentally, and I can likely put out more watts at a lower mental cost than on the flats. Much easier to stay on the gas, so to speak.

Don't worry about the length of the recoveries if you go hard up and recover down. Chantry flats, my local interval hill, takes me 18-22' to climb, depending on fitness and weight, and about 6-7' to descend. It is what is, but I can get in 60' of FTP+ time/1500kj, 145-150 TSS in a 1:45 workout. Just can't be beat.

Rubin, I think you're down in Whittier, but the Santa Fe Dam is the PERFECT outdoor interval venue. Back in the day my buddies and I did interval training up there every Tues and Thursday AM. I called the Santa Fe Missle Range. Horseshoe shape, pool table flat, 3 miles long from end to end and you can see all of it at a glance.

MoJoe

Posted By Rubin Johnson on 11 Jan 2011 05:22 PM

@Nemo and William

they still output the intensity factor IF. Since IF = NP/AP, they have implicitly provided the NP... 

 

@Rubin, 

Picking a nit,  VI = NP/AP, and IF = NP/FTP.  I can't speak to whether WKO2.2 (or 3.0) implicitly provides NP based on giving IF.  However, a logical guesstimate, since they do not calculate NP because of the too-short interval, perhaps they approximate NP by substituting AP to get the formula IF ~= AP/FTP.

trijedi

@Joe

You're right, of course.  IF = NP/FTP.  In WKO 2.2, I'll get something like the data below...

Lap 2:

Duration:   2:33

Work:       37 kJ

TSS:       6.2 (intensity factor 1.208)

Norm Power: n/a

VI:         n/a

I have had rides with the same AP for the short segment but a vastly different IF, so it doesn't look like WKO is approximating IF by using AP. I suspect they are initializing the first 30 second moving average in a way that is easily skewed which is why they don't want to print the NP or VI numbers. Still there is an implicit NP for the short segment. I am going to go along with the consensus and just use AP for these VO2 intervals.

 

Part of the problem for me is that I have been doing my workouts outside with the Garmin 310XT as my bike computer. One of its peculiarities is that it doesn't include zeros when it does average power. That means if you are forced to slow down, or go down a grade, or stop producing power in any way, then the device will show an average power that is higher than your actual power. So it is possible to think you have nailed the interval when in fact you are a little bit below. For the LT workouts, I look straight at the IF. I did that with the VO2 workouts at first and noticed that although the IF was at 1.2+, there were segments where the average power was less than 1.2. That was the reason for the thread. Thanks for paying attention to my rambling...